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MEDIUM severity

CVE-2026-45366 — @utcp/http

MEDIUM

CVE-2026-45366 is a medium-severity (CVSS 4.7) Server-Side Request Forgery (SSRF) vulnerability in @utcp/http. A fix is available for @utcp/http — see the affected versions and patch details below.

@utcp/http: SSRF via attacker-controlled OpenAPI servers[0].url in HTTP communication protocol

Published
May 14, 2026
Updated
Sep 10, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Sep 27, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45366.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs8th percentile — riskier than 8% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-45366 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

21other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
@utcp/httpnpm
2Kdownloads / week

Description

Summary

The @utcp/http package is vulnerable to a blind Server-Side Request Forgery (SSRF) caused by a trust-boundary inconsistency between manual discovery and tool invocation. registerManual() validates the discovery URL against an HTTPS / loopback allowlist, but callTool() reuses the resolved toolCallTemplate.url directly without revalidating, and the OpenApiConverter blindly trusts whatever servers[0].url an attacker-hosted spec declares. An attacker who hosts a malicious OpenAPI spec on a legitimate HTTPS endpoint can declare e.g. servers: [{ url: "http://127.0.0.1:9090" }] or servers: [{ url: "http://169.254.169.254" }]; the converter then produces tools whose URL points at internal services on the agent host.

A separate prefix-bypass also affected the discovery-time check: the previous startsWith('http://localhost') guard let URLs like http://localhost.evil.com through.

Sister advisory

This is the npm/TypeScript counterpart of GHSA-39j6-4867-gg4w / CVE-2026-44661 on the Python utcp-http package. Same vulnerability, same fix shape, same reporter.

Versions and patch state

  • @utcp/http <= 1.1.1 — vulnerable. Both the loopback-redirect (http://127.0.0.1) and the non-loopback internal-IP variants (e.g. http://169.254.169.254, http://10.0.0.5) succeed. Note: the streamable_http and sse callToolStreaming paths in 1.1.1 are TODO placeholders and don't actually fetch URLs, so the runtime SSRF surface in these protocols is currently confined to discovery — a future implementation must also call ensureSecureUrl before issuing the request.
  • @utcp/http 1.1.2 — full fix. Runtime revalidation in callTool closes the non-loopback variants; the OpenApiConverter rejects, at conversion time, any spec fetched from a non-loopback source that declares a loopback servers[0].url, closing the loopback-redirect variant.

Impact

A remote attacker who can convince the agent (via the LLM context, prompt injection, or a tool-discovery surface) to register their HTTPS OpenAPI URL can:

  • Map internal networks behind the agent.
  • Read AWS/GCP IAM credentials from cloud metadata endpoints (http://169.254.169.254, http://metadata.google.internal).
  • Reach unauthenticated internal services exposed on loopback (Elasticsearch, Redis HTTP, internal admin panels, the agent's own HTTP server).
  • Have responses returned to the LLM, which combined with prompt injection enables exfiltration back to the attacker.

Patch

Commit on dev: 21f63e6.

New helper packages/http/src/_security.ts exposes isSecureUrl, isLoopbackUrl, ensureSecureUrl. Hostname-based validation closes the prefix bypass (http://localhost.evil.com → rejected). All three protocols' registerManual now call ensureSecureUrl(url, 'manual discovery'); callTool re-checks the resolved URL with ensureSecureUrl(url, 'tool invocation') immediately before the axios request. OpenApiConverter rejects remote spec → loopback server.

Workarounds

For users who cannot upgrade immediately:

  • Refuse to call registerManual with any URL controlled by an untrusted party, even over HTTPS.
  • Restrict outbound network access from the host running the agent so internal addresses (RFC1918, 169.254.0.0/16, loopback) are unreachable.

Credit

Discovered and reported by @YLChen-007 against the Python sibling implementation (universal-tool-calling-protocol/python-utcp#83). The TypeScript port shared the same code shape and the same vulnerability.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npm@utcp/httpall versions1.1.2npm install @utcp/http@1.1.2

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @utcp/http, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update @utcp/http to 1.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45366 is resolved across your whole dependency graph.

  3. Workarounds

    Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

Frequently Asked Questions

## Summary The `@utcp/http` package is vulnerable to a blind Server-Side Request Forgery (SSRF) caused by a trust-boundary inconsistency between manual discovery and tool invocation. `registerManual()` validates the discovery URL against an HTTPS / loopback allowlist, but `callTool()` reuses the resolved `toolCallTemplate.url` directly without revalidating, and the `OpenApiConverter` blindly trusts whatever `servers[0].url` an attacker-hosted spec declares. An attacker who hosts a malicious OpenAPI spec on a legitimate HTTPS endpoint can declare e.g. `servers: [{ url: "http://127.0.0.1:9090"
O3 Security · Impact-Aware SCA

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CVE-2026-45366: @utcp/http (Medium 4.7) | O3 Security